WO2023015437A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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Publication number
WO2023015437A1
WO2023015437A1 PCT/CN2021/111736 CN2021111736W WO2023015437A1 WO 2023015437 A1 WO2023015437 A1 WO 2023015437A1 CN 2021111736 W CN2021111736 W CN 2021111736W WO 2023015437 A1 WO2023015437 A1 WO 2023015437A1
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Prior art keywords
active layer
pole piece
current collector
binder
active material
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PCT/CN2021/111736
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English (en)
French (fr)
Inventor
江兵
刘涛
周丰
张青文
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN202180031189.9A priority Critical patent/CN115552657B/zh
Priority to PCT/CN2021/111736 priority patent/WO2023015437A1/zh
Publication of WO2023015437A1 publication Critical patent/WO2023015437A1/zh
Priority to US18/436,115 priority patent/US20240274801A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemical energy storage, in particular to electrochemical devices and electronic devices.
  • the volumetric energy density of electrochemical devices has always been a bottleneck restricting the development of electrochemical devices.
  • electrochemical devices for example, lithium-ion batteries
  • the active material layer at the edge of the pole piece is prone to loosening and falling powder, which is not conducive to the improvement of the energy density of the pole piece, and may cause lithium precipitation. away from risk. Therefore, further improvements are expected.
  • the electrochemical device includes a first pole piece, a second pole piece electrically different from the first pole piece, and an electrode disposed between the first pole piece and the second pole piece. isolation film between.
  • the first pole piece includes a current collector, a tab and an active layer, and the tab is electrically connected to the current collector and protrudes from the current collector.
  • the active layer is arranged on the surface of the current collector, and the active layer includes a first active layer and a second active layer.
  • the first active layer is located on the side of the second active layer facing the tab, and is adjacent to or partially overlapped with the second active layer.
  • the first active layer and the second active layer extend in a strip shape.
  • the cohesion of the first active layer is greater than the cohesion of the second active layer.
  • the first direction is the direction in which the tab protrudes from the current collector
  • the third direction is the thickness direction of the negative electrode sheet
  • the second direction is perpendicular to the plane where the first direction and the second direction are located.
  • the cohesive force of the first active layer is greater than that of the second active layer, so that the edge of the pole piece is not easy to drop powder, which can allow the further improvement of the compaction density of the pole piece, thereby improving the volumetric energy density of the electrochemical device , and reduce the risk of lithium analysis.
  • the cohesive force of the first active layer is 10N/m to 20N/m
  • the cohesive force of the second active layer is 4N/m to 8N/m, within this range, the powder dropping phenomenon at the edge of the pole piece can be obtained Significantly improved, and will not bring adverse effects on the conductivity of the pole piece and the energy density of the electrochemical device.
  • the width of the first active layer is 5 mm to 20 mm, and the width of the second active layer is 10 mm to 300 mm.
  • the bonding force between the first active layer and the current collector is greater than the bonding force between the second active layer and the current collector.
  • the bonding force between the first active layer and the current collector is 8N/m to 20N/m, and the bonding force between the second active layer and the current collector is 1N/m to 8N/m.
  • the first active layer includes a first active material and a first binder
  • the second active layer includes a second active material and a second binder
  • the powder compacted density of the first active material is greater than that of the first active material. 2.
  • the powder compaction density of the active material By increasing the powder compaction density of the first active material at the edge of the pole piece, the coating weight per unit area can be increased, which can not only improve the phenomenon of powder dropping at the edge of the pole piece, but also increase the energy density of the electrochemical device.
  • the first active layer includes a first active material and a first binder
  • the second active layer includes a second active material and a second binder
  • the first binder in the first active layer The mass fraction is greater than the mass fraction of the second binder in the second active layer.
  • a higher binder content can increase the cohesiveness between the active material particles and the active material particles, and improve the powder dropping phenomenon at the edge of the pole piece.
  • the first active layer includes a first active material and a first binder
  • the second active layer includes a second active material and a second binder
  • the powder compacted density of the first active material is greater than that of the first active material.
  • the mass fraction of the first binder in the first active layer is greater than the mass fraction of the second binder in the second active layer.
  • the powder compaction density and binder content of the active material in the first active layer are increased to further improve the powder falling phenomenon at the edge of the pole piece.
  • the powder compacted density of the first active material is 1.8 g/cm 3 to 2.5 g/cm 3
  • the powder compacted density of the second active material is 1 g/cm 3 to 1.7 g/cm 3 .
  • the mass fraction of the first binder in the first active layer is 15% to 30%, and the mass fraction of the second binder in the second active layer is 1% to 10%.
  • the powder compacted density of the first active material is 1.8 g/cm 3 to 2.5 g/cm 3
  • the powder compacted density of the second active material is 1 g/cm 3 to 1.7 g/cm 3
  • the mass fraction of the first binder in the first active layer is 15% to 30%
  • the mass fraction of the second binder in the second active layer is 1% to 10%.
  • the first active material and the second active material each independently include natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, silicon oxide, Li - at least one of Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithium titanate, Li-Al alloy or metallic lithium.
  • the first binder and the second binder each independently include polyacryl alcohol, polyacrylic acid, polyacrylate, polyimide, polyamideimide, styrene-butadiene rubber, polyvinylidene fluoride At least one of ethylene, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, water-based acrylic resin or carboxymethyl cellulose salt.
  • the tab is integrally formed with the current collector.
  • An embodiment of the present application also provides an electronic device, including the above-mentioned electrochemical device.
  • the edge of the pole piece is not prone to powder dropping, which in turn allows the further improvement of the compaction density of the pole piece, thereby improving the performance of the electrochemical device. Volume energy density, and reduce the risk of lithium analysis.
  • Figure 1 shows a top view of a first pole piece of some embodiments of the present application
  • Fig. 2 shows a cross-sectional view of the first pole piece shown in Fig. 1 along the direction AA'.
  • Some embodiments of the present application provide an electrochemical device, the electrochemical device includes a first pole piece, a second pole piece, and a separator arranged between the first pole piece and the second pole piece, wherein the first pole piece The electric properties of the pole piece and the second pole piece are different.
  • the first pole piece includes a current collector, a tab and an active layer, the tab is electrically connected to the current collector and protrudes from the current collector, and the active layer is disposed on the surface of the current collector.
  • the active layer is disposed on one side of the current collector, and in other embodiments, the active layer is disposed on both sides of the current collector.
  • FIG. 1 a top view of a first pole piece in an unfolded state is shown in some embodiments.
  • Fig. 2 a cross-sectional view of the first pole piece shown in Fig. 1 along the direction AA' is shown.
  • the active layer 102 is disposed on both sides of the current collector 101 , and the active layer 102 includes a first active layer 1021 and a second active layer 1022 . As shown in FIG.
  • the first active layer 1021 is located on the side of the second active layer 1022 facing the tab 103 (that is, along the first direction, the first active layer 1021 is closer than the second active layer 1022 Close to the side where the current collector protrudes from the tab), and is adjacent to or partially overlapped with the second active layer 1022; along the second direction y, the first active layer 1021 and the second active layer 1022 extend in a strip shape, as shown in FIG. 1, the first active layer 1021 and the second active layer 1022 are rectangular strips and extend parallel to each other along the second direction y.
  • the above-mentioned directions are defined as follows: in a three-dimensional rectangular coordinate system, the first direction x is the direction in which the tab protrudes from the current collector, the third direction z is the thickness direction of the first pole piece, and the second direction y is vertical in the plane where the first direction x and the second direction y lie.
  • the above “adjacent” means that the first active layer 1021 and the second active layer 1022 do not overlap in the third direction z (that is, the thickness direction of the pole piece), and in the first direction x ( That is, the direction in which the tabs protrude from the current collector) is not spaced. In this way, the contact area between the first active layer 1021 and the second active layer 1022 can be prevented from being too thick, thereby affecting the local thickness of the pole piece, and adversely affecting the flatness of the battery cell.
  • partial overlap means that along the third direction z (ie, the thickness direction of the pole piece), the projected areas of the first active layer 1021 and the second active layer 1022 on the current collector have an overlapping area, that is, in the current collector.
  • the first active layer 1021 may be superimposed on the second active layer 1022
  • the second active layer 1022 may be superimposed on the first active layer 1021 .
  • the metal foil is selected as the current collector, and the active slurry is coated on the surface of the metal foil, and there will be a coating area coated with the active slurry on the surface of the metal foil And the empty foil area that is not coated with active paste, the empty foil area can be used to die-cut tabs or solder tabs.
  • the coating area In order to increase the energy density of the battery, before the above-mentioned coated foil is cut into pole pieces, it is necessary to compact the coating area to increase the coating weight per unit area, that is, to increase the compaction density of the active material layer.
  • the active material layer will be easily loosened due to the vertical stress of the compaction process, and powder falling will occur, which will lead to separation.
  • the coating weight per unit area at the edge of the pole piece after cutting is reduced, thus reducing the energy density of the battery, and there is a risk of lithium precipitation.
  • first active slurries and second active slurries are respectively coated on the surface of the metal foil to form a first coating coated with the first active slurries.
  • Area, the second coating area coated with the second active slurry, and the first coating area is located on the side of the second coating area close to the empty foil area, that is, the edge of the second active layer 1022 is set.
  • the first active layer 1021 by making the cohesive force of the first active layer 1021 greater than the cohesive force of the second active layer 1022, in the compaction process, the first active layer 1021 is not easy to loose due to its larger cohesive force, which reduces edge drop. The appearance of powder phenomenon.
  • the edge of the pole piece has a coating weight per unit area equivalent to that of the middle of the pole piece, which is beneficial to the improvement of the energy density of the electrochemical device.
  • the compaction density of the pole piece can be further improved, thereby increasing the volumetric energy density of the electrochemical device.
  • the cohesion of the first active layer is 10 N/m to 20 N/m, and the cohesion of the second active layer is 4 N/m to 8 N/m. If the cohesive force of the first active layer is too small, the effect on improving the powder shedding at the edge of the first pole piece is relatively limited; if the cohesive force of the first active layer is too large, the compaction density of the active layer is usually required to be too large or more If the compaction density is too high, it will easily affect the penetration of the electrolyte and the conductivity of the pole piece; and the use of more binder means that the amount of active materials will be reduced, which will affect the conductivity and electrochemical performance of the pole piece. The energy density of the device.
  • the cohesion of the first active layer is 10N/m, 12N/m, 15N/m, 18N/m, 20N/m or a range composed of any two of the above values.
  • the cohesion of the second active layer is 4N/m, 6N/m, 8N/m or a range composed of any two of the above values.
  • the width of the first active layer is 5 mm to 20 mm, and the width of the second active layer is 10 mm to 300 mm. If the width of the first active layer is too small, its effect on improving the edge powder shedding of the pole piece is relatively limited; if the width of the first active layer is too large, when the content of the binder in the first active layer is high , will adversely affect the volumetric energy density of the electrochemical device.
  • the width of the first active layer is 5 mm, 12 mm, 15 mm, 18 mm, 20 mm or a range composed of any two of the above values.
  • the width of the second active layer is 10mm, 30mm, 50mm, 80mm, 100mm, 120mm, 150mm, 180mm, 300mm or a range composed of any two of the above values.
  • the bonding force between the first active layer and the current collector is greater than the bonding force between the second active layer and the current collector. In this way, the first active layer is less likely to fall off from the current collector, and it can more stably play the role of improving the edge powder drop of the pole piece.
  • the bonding force between the first active layer and the current collector is 8N/m to 20N/m, and the bonding force between the second active layer and the current collector is 1N/m to 8N/m. If the bonding force between the first active layer and the current collector is too small, the first active layer will easily fall off from the current collector, which will affect the performance of the first active layer to improve the powder drop at the edge of the pole piece; if the first active layer If the bonding force between the layer and the current collector is too large, a higher binder content in the first active layer is usually required, which is not conducive to improving the volumetric energy density of the electrochemical device.
  • the bonding force between the first active layer and the current collector is 8N/m, 10N/m, 12N/m, 15N/m, 18N/m, 20N/m or any two values above composed range. In some embodiments, the bonding force between the second active layer and the current collector is 1N/m, 3N/m, 5N/m, 6N/m, 8N/m, or a range consisting of any two values above .
  • the first active layer includes a first active material and a first binder
  • the second active layer includes a second active material and a second binder
  • the powder compacted density of the first active material is greater than that of the first active material. 2.
  • the powder compaction density of the active material The higher the compacted density of the powder, the higher the weight of the active material per unit volume, using the same pressure. Therefore, when performing compaction, under the same cold pressing conditions, since the first active material at the edge of the pole piece has a higher powder compaction density, the edge of the pole piece can accommodate more first active materials. without falling powder. Under this condition, the pressure in the compaction process can be increased. Under the condition of increased pressure, the edge of the pole piece will not appear to drop powder, so that the coating weight per unit area and the compaction density of the pole piece can be increased. It is improved, which is beneficial to increase the energy density of the electrochemical device.
  • the mass fraction of the first binder in the first active layer is greater than the mass fraction of the second binder in the second active layer.
  • the powder compacted density of the first active material is 1.8 g/cm 3 to 2.5 g/cm 3
  • the powder compacted density of the second active material is 1 g/cm 3 to 1.7 g/cm 3 .
  • the powder compacted density of the first active material is 1.8g/cm 3 , 2.0g/cm 3 , 2.2g/cm 3 , 2.5g/cm 3 or a combination of any two values above. scope.
  • the powder compacted density of the second active material is 1 g/cm 3 , 1.2 g/cm 3 , 1.5 g/cm 3 , 1.7 g/cm 3 or a range consisting of any two values above .
  • the mass fraction of the first binder in the first active layer is 15% to 30%, and the mass fraction of the second binder in the second active layer is 1% to 10%. If the mass fraction of the first binder in the first active layer is too small, it is not conducive to the promotion of the cohesive force of the first active layer, and the effect of improving the edge powder shedding of the pole piece is relatively limited; if the first binder is in the first active layer If the mass fraction in the active layer is too large, it will be unfavorable to increase the volumetric energy density of the electrochemical device. In some embodiments, the mass fraction of the first binder in the first active layer is 15%, 20%, 25%, 30%, or a range composed of any two values above. In some embodiments, the mass fraction of the second binder in the second active layer is 1%, 3%, 5%, 8%, 10%, or a range composed of any two values above.
  • the first pole piece is a negative pole piece
  • the active layer is a negative pole active layer
  • the current collector is a negative pole current collector.
  • the negative pole current collector can be made of copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, At least one of nickel foam, copper foam, composite current collectors or carbon-based current collectors.
  • the second pole piece is a positive pole piece.
  • the first active material and the second active material each independently include natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, silicon oxides (such as At least one of SiO x (0 ⁇ x ⁇ 2)), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithium titanate, Li-Al alloy or metallic lithium.
  • the first pole piece is a positive pole piece
  • the active layer is a positive pole active layer
  • the current collector is a positive pole current collector
  • the positive pole current collector includes aluminum foil.
  • the second pole piece is a negative pole piece.
  • the first active material and the second active material each independently include lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, phosphoric acid At least one of sodium vanadyl, lithium vanadate, lithium manganate, lithium nickelate, lithium nickel-cobalt manganate, lithium-rich manganese-based materials or lithium nickel-cobalt aluminate.
  • the first binder and the second binder each independently include polyacryl alcohol, polyacrylic acid, polyacrylate, polyimide, polyamideimide, styrene-butadiene rubber, polyvinylidene fluoride At least one of ethylene, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, water-based acrylic resin or carboxymethyl cellulose salt.
  • the first active layer and the second active layer each further include a conductive agent.
  • the conductive agent includes at least one of conductive carbon black, Ketjen black, graphite flakes, graphene, carbon nanotubes, or carbon fibers.
  • the tab is integrally formed with the current collector 101 . In this way, it is beneficial to simplify the preparation process of the electrochemical device, and is also beneficial to the stable connection of the tabs.
  • the electrochemical device may further include an electrolyte, and the electrolyte may be at least one of a gel electrolyte, a solid electrolyte, and an electrolytic solution.
  • the electrolyte includes a lithium salt and a non-aqueous solvent.
  • lithium salts may include LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , At least one of LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB, or lithium difluoroborate.
  • the non-aqueous solvent may be at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.
  • the isolation film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.
  • polyethylene and polypropylene which have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect.
  • the surface of the isolation membrane may also include a porous layer, the porous layer is arranged on at least one surface of the isolation membrane, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from alumina (Al 2 O 3 ), Silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium oxide (HfO 2 ), tin oxide (SnO 2 ), cerium oxide (CeO 2 ), nickel oxide (NiO), oxide Zinc (ZnO), calcium oxide (CaO), zirconia (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or sulfuric acid at least one of barium.
  • the porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion
  • the electrochemical device is prepared by laminating the first pole piece, the separator and the second pole piece and then winding to obtain a wound electrode assembly. In some embodiments, the electrochemical device is prepared by stacking the first pole piece, the separator and the second pole piece to obtain a laminated electrode assembly.
  • the electrochemical device includes a lithium-ion battery, although the present application is not limited thereto.
  • the positive pole piece, the separator, and the negative pole piece are prepared as a wound-type electrode assembly, which is then packed into, for example, an aluminum-plastic film for packaging, and the electrolyte is injected. Formation, packaging, that is, into a lithium-ion battery. Then, performance tests were performed on the prepared lithium-ion batteries.
  • Embodiments of the present application also provide electronic devices including the above electrochemical device.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Unmanned aerial vehicles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • Preparation of the positive electrode sheet mix the positive active material lithium cobaltate, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) according to the weight ratio of 97:1.4:1.6, and add N-methylpyrrolidone (NMP) As a solvent, stir well.
  • the slurry solid content is 72wt%) is uniformly coated on the aluminum foil of the positive electrode current collector with a coating thickness of 80 ⁇ m, dried at 85°C, and then cold-pressed, cut into pieces, and slit, and vacuum-coated at 85°C Drying under the same conditions for 4 hours to obtain a positive electrode sheet.
  • the negative active material natural graphite, the dispersant lithium carboxymethyl cellulose, and the binder polyacrylic acid are mixed with water in a weight ratio of 8:0.2:1.8 until the slurry is uniformly dispersed to obtain the first slurry material.
  • the negative electrode active material natural graphite, the dispersant lithium carboxymethyl cellulose, and the binder polyacrylic acid are added with water in a weight ratio of 9:0.2:0.8 and stirred until the slurry is uniformly dispersed to obtain the second slurry.
  • Copper foil with a thickness of 10 ⁇ m is used as the negative electrode current collector, and the first slurry and the second slurry are respectively coated on the surface of the negative electrode current collector by using the zebra coating process (that is, interval coating) to form a coating area, and expose the uncoated
  • the isolation membrane is polyethylene (PE) with a thickness of 7 ⁇ m.
  • Lithium-ion battery preparation stack the positive pole piece, the separator, and the negative pole piece in order, so that the separator is in the middle of the positive pole piece and the negative pole piece to play the role of isolation, and wind up to obtain the electrode assembly.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium-ion battery is obtained through chemical formation, degassing, trimming and other processes.
  • Example 2 The difference between Example 2 and Example 1 lies in the composition of the first slurry, which is: the weight ratio of natural graphite, dispersant lithium carboxymethyl cellulose, and binder polyacrylic acid is 7.8:0.2:2.
  • Example 3 The difference between Example 3 and Example 1 lies in the composition of the first slurry, the weight ratio of natural graphite, dispersant lithium carboxymethyl cellulose, and binder polyacrylic acid is 7.6:0.2:2.2.
  • the difference between embodiment 4 and embodiment 1 is that the dispersant in the second slurry is sodium carboxymethyl cellulose, and the binder is styrene-butadiene rubber; in addition, the composition of the first slurry is different, being: artificial graphite, dispersed
  • the weight ratio of sodium carboxymethyl cellulose and binder styrene-butadiene rubber is 9:0.2:0.8, and the compacted density of artificial graphite powder is 1.85g/cm 3 .
  • Example 5 The only difference between Example 5 and Example 4 is that the powder compacted density of the artificial graphite is 1.95 g/cm 3 .
  • Example 6 The only difference between Example 6 and Example 4 is that the powder compacted density of the artificial graphite is 2 g/cm 3 .
  • composition of the first slurry is different, being: the weight ratio of artificial graphite, dispersant sodium carboxymethyl cellulose, binder styrene-butadiene rubber is 8: 0.2: 1.8, artificial graphite
  • the powder compacted density is 1.85g/cm 3 .
  • Example 8 The only difference between Example 8 and Example 7 is that the powder compacted density of the artificial graphite is 2 g/cm 3 .
  • Comparative Example 2 The only difference between Comparative Example 2 and Comparative Example 1 is that the active material of the second slurry is changed from natural graphite to hard carbon, and the compacted density of hard carbon powder is 1.2 g/cm 3 .
  • Comparative Example 3 and Comparative Example 1 The only difference between Comparative Example 3 and Comparative Example 1 is that the binder in the second slurry was changed from styrene-butadiene rubber to sodium polyacrylate.
  • the brand of instrument used for testing the adhesion between the negative electrode active layer and the negative electrode current collector is Instron, and the model is 33652.
  • the indicator light is on, adjust the limit block to a suitable position, fold the green glue up and slide it 40mm, the sliding rate is 50mm/min, and test the negative electrode at 180° (that is, stretching in the opposite direction) Cohesion between active layers.
  • the powder density tester (test mold (CARVER#3619 (13mm)); the test equipment is Sansi Zongheng UTM7305, and the mold is placed on the upper and lower platens of the equipment In the middle of the device, click the run button in the device, and the device will run according to the set parameters.
  • the pressure point of the device is released to 5T, record the displacement value at this time. This is the thickness of the sample under this pressure (the pressure increase rate is 10mm/min, the pressurization hold time is 30s, the pressure release rate is 30mm/min, the pressure release hold time is 10s).
  • the compacted density of the powder can be calculated by the following formula:
  • Table 1 shows the respective parameters and evaluation results of the respective Examples 1 to 8 and Comparative Examples 1 to 3.
  • Example 4 By comparing Example 4 and Comparative Example 1, it can be seen that, with respect to the negative electrode sheet containing only the second active layer, by setting an additional first active layer, and making the cohesion of the first active layer greater than the cohesion of the second active layer , can significantly improve the edge powder drop of the negative electrode sheet.
  • Comparative Examples 1-3 when the same active layer was disposed in the middle and the edge of the current collector, obvious powder dropping occurred.
  • Comparative Example 2 compared with Comparative Example 1, when the type of active material of the first active layer and the compacted density of the powder were changed, obvious powder dropping still occurred.
  • Comparative Example 3 relative to Comparative Example 1, when the binder in the first active layer was changed, significant powder dropping still occurred. It can be seen that when the compacted density of the powder of the first active material is low, the amount of the binder in the first active material is less, and the edge of the pole piece is easy to drop powder.

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Abstract

本申请提供了电化学装置和电子装置。该电化学装置包括第一极片、与第一极片电性不同的第二极片和设置于第一极片与第二极片之间的隔离膜。第一极片包括集流体、极耳和活性层。极耳与集流体电连接并伸出于集流体。活性层设置于集流体的表面，活性层包括第一活性层和第二活性层。沿第一方向，第一活性层位于第二活性层朝向极耳的一侧，并与第二活性层相邻接或部分重叠。沿第二方向，第一活性层和第二活性层呈带状延伸。第一活性层的内聚力大于第二活性层的内聚力。通过使第一活性层的内聚力大于第二活性层的内聚力，使得第一极片更不易发生边缘掉粉。

Description

电化学装置和电子装置 技术领域
本申请涉及电化学储能领域，尤其涉及电化学装置和电子装置。
背景技术
电化学装置(例如，锂离子电池)的体积能量密度一直是制约电化学装置发展的瓶颈，为了提高电化学装置的体积能量密度，通常需要提高极片压实密度。然而，在提高极片压实密度的条件下，由于较高的压力，处于极片边缘的活性物质层容易发生松散而掉粉，从而不利于极片能量密度的提高，并有可能引发析锂离风险。因此，期待进一步的改进。
发明内容
本申请的一些实施例提供了一种电化学装置，该电化学装置包括第一极片、与第一极片电性不同的第二极片和设置于第一极片与第二极片之间的隔离膜。第一极片包括集流体、极耳和活性层，极耳与集流体电连接并伸出于集流体。活性层设置于集流体的表面，活性层包括第一活性层和第二活性层。沿第一方向，第一活性层位于第二活性层朝向极耳的一侧，并与第二活性层相邻接或部分重叠。沿第二方向，第一活性层和第二活性层呈带状延伸设置。第一活性层的内聚力大于第二活性层的内聚力。在三维直角坐标系中，第一方向为极耳伸出集流体的方向，第三方向为负极极片的厚度方向，第二方向垂直于第一方向和第二方向所在的平面。
本申请通过使第一活性层的内聚力大于第二活性层的内聚力，使得极片边缘不易出现掉粉现象，进而可以允许极片的压实密度的进一步提升，从而提高电化学装置的体积能量密度，并降低析锂风险。
在一些实施例中，第一活性层的内聚力为10N/m至20N/m，第二活性层的内聚力为4N/m至8N/m，在此范围内，极片边缘的掉粉现象可以得到显著改善，并且也不会给极片的导电性和电化学装置的能量密度带来不利影响。
在一些实施例中，第一活性层的宽度为5mm至20mm，第二活性层的宽度为10mm至300mm。
在一些实施例中，第一活性层与集流体之间的粘结力大于第二活性层与集流体之间的粘结力。如此设置，极片边缘的活性层与集流体之间的粘结性更好，更不容易从集流体上脱落。
在一些实施例中，第一活性层与集流体之间的粘结力为8N/m至20N/m，第二活性层与集流体之间的粘结力为1N/m至8N/m。
在一些实施例中，第一活性层包括第一活性材料和第一粘结剂，第二活性层包括第二活性材料和第二粘结剂，第一活性材料的粉体压实密度大于第二活性材料的粉体压实密度。通过提高极片边缘的第一活性材料的粉体压实密度，可以提高其单位面积涂覆重量，不仅可以改善极片边缘的掉粉现象，同时也能提高电化学装置的能量密度。
在一些实施例中，第一活性层包括第一活性材料和第一粘结剂，第二活性层包括第二活性材料和第二粘结剂，第一粘结剂在第一活性层中的质量分数大于第二粘结剂在第二活性层中的质量分数。较高的粘结剂含量可以增加活性材料颗粒与活性材料颗粒之间的粘结性，改善极片边缘的掉粉现象。
在一些实施例中，第一活性层包括第一活性材料和第一粘结剂，第二活性层包括第二活性材料和第二粘结剂，第一活性材料的粉体压实密度大于第二活性材料的粉体压实密度，第一粘结剂在第一活性层中的质量分数大于第二粘结剂在第二活性层中的质量分数。提高第一活性层中的活性材料的粉体压实密度和粘结剂的含量，进一步改善极片边缘的掉粉现象。
在一些实施例中，第一活性材料的粉体压实密度为1.8g/cm 3至2.5g/cm 3，第二活性材料的粉体压实密度为1g/cm 3至1.7g/cm 3。
在一些实施例中，第一粘结剂在第一活性层中的质量分数为15％至30％，第二粘结剂在第二活性层中的质量分数为1％至10％。
在一些实施例中，第一活性材料的粉体压实密度为1.8g/cm 3至2.5g/cm 3，第二活性材料的粉体压实密度为1g/cm 3至1.7g/cm 3，第一粘结剂在第一活性层中的质量分数为15％至30％，第二粘结剂在第二活性层中的质量分数为1％至10％。
在一些实施例中，第一活性材料和第二活性材料各自独立地包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、硅氧化物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、钛酸锂、Li-A1合金或金属锂中的至少一种。
在一些实施例中，第一粘结剂和第二粘结剂各自独立地包括聚丙烯醇、聚丙烯酸、聚丙烯酸盐、聚酰亚胺、聚酰胺酰亚胺、丁苯橡胶、聚偏氟乙烯、聚偏二氟乙烯、聚四氟乙烯、聚乙烯醇缩丁醛、水性丙烯酸树脂或羧甲基纤维素盐中的至少一种。
在一些实施例中，极耳与集流体一体成型。
本申请的实施例还提供了一种电子装置，包括上述电化学装置。
本申请的实施例通过使第一活性层的内聚力大于第二活性层的内聚力，使得极片边缘不易出现掉粉现象，进而可以允许极片的压实密度的进一步提升，从而提高电化学装置的体积能量密度，并降低析锂风险。
附图说明
图1示出了本申请的一些实施例的第一极片的俯视图；
图2示出了图1所示的第一极片沿AA’方向的截面图。
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
本申请的一些实施例提供了一种电化学装置，该电化学装置包括第一极片、第二极片和设置于第一极片与第二极片之间的隔离膜，其中，第一极片与第二极片的电性不同。
在一些实施例中，第一极片包括集流体、极耳和活性层，极耳与集流体电连接并伸出于集流体，活性层设置在集流体的表面。
在一些实施例中，活性层设置于集流体的一侧表面上，在其他一些实施例中，活性层设置于集流体的双侧表面上。
如图1所示，示出了一些实施例中的呈展开状态的第一极片的俯视图。如图2所示，示出了图1所示的第一极片沿AA’方向的截面图。请参考图1 和图2，活性层102设置于集流体101的双侧表面上，活性层102包括第一活性层1021和第二活性层1022。如图1所示，沿第一方向x，第一活性层1021位于第二活性层1022朝向极耳103的一侧(即沿第一方向，第一活性层1021相比第二活性层1022更靠近集流体伸出极耳的一侧)，并与第二活性层1022相邻接或部分重叠；沿第二方向y，第一活性层1021和第二活性层1022呈带状延伸，如图1所示，第一活性层1021和第二活性层1022均为矩形的条带状，且相互平行地沿第二方向y延伸。
本申请中，对上述方向做以下定义：在三维直角坐标系中，第一方向x为极耳伸出集流体的方向，第三方向z为第一极片的厚度方向，第二方向y垂直于第一方向x和第二方向y所在的平面。
应当理解的是，上述的“相邻接”指的是第一活性层1021与第二活性层1022在第三方向z上(即极片的厚度方向)不重叠，在第一方向x上(即极耳伸出集流体的方向)不间隔。如此，可以防止第一活性层1021和第二活性层1022的接触区域过厚从而影响极片的局部厚度，给电芯的平整性带来不利影响。上述的“部分重叠”指的是沿第三方向z(即极片的厚度方向)，第一活性层1021和第二活性层1022在集流体上的投影面积有重叠区域，即在集流体的表面上，在第一活性层和第二活性层的接触区域，可以为第一活性层1021叠加在第二活性层1022上，也可以为第二活性层1022叠加在第一活性层1021上。
通常，在极片制备的涂布工序中，选择金属箔材作为集流体，将活性浆料涂布在金属箔材表面，在金属箔材的表面会存在涂覆有活性浆料的涂覆区和未涂覆活性浆料的空箔区，空箔区可用来模切极耳或者焊接极耳。为了提高电池的能量密度，在将上述涂布后的箔材分切为极片之前，需要对涂覆区进行压实来提高单位面积的涂覆重量，即提高活性材料层的压实密度。由于在涂覆区的边缘，即在涂覆区靠近空箔区的一侧，活性材料层会受到压实过程的垂向应力而容易松散，出现掉粉现象，掉粉现象的出现会导致分切之后的极片边缘位置的单位面积涂布重量减小，因此降低了电池的能量密度，并且存在析锂的风险。
本申请中，在涂布工序中，将两种不同的第一活性浆料和第二活性浆料分别涂布在金属箔材表面，形成了涂覆有第一活性浆料的第一涂覆区，涂覆 有第二活性浆料的第二涂覆区，并且，将第一涂覆区位于第二涂覆区靠近空箔区的一侧，即在第二活性层1022的边缘设置了第一活性层1021，通过使第一活性层1021的内聚力大于第二活性层1022的内聚力，在压实过程中，第一活性层1021由于其较大的内聚力而不容易松散，减少了边缘掉粉现象的出现。因此，在制备得到的极片上，极片边缘具有和极片中部相当的单位面积涂布重量，有利于电化学装置的能量密度的提高。同时，由于边缘掉粉现象的发生可能性的降低，进而可以允许极片的压实密度的进一步提升，从而提高电化学装置的体积能量密度。
在一些实施例中，第一活性层的内聚力为10N/m至20N/m，第二活性层的内聚力为4N/m至8N/m。如果第一活性层的内聚力太小，则对改善第一极片边缘掉粉的作用相对有限；如果第一活性层的内聚力太大，则通常要求活性层的压实密度过大或采用更多的粘结剂，压实密度过大容易影响电解液的渗透，影响极片的导电性；而采用更多的粘结剂意味着要减少活性材料的用量，影响极片的导电性和电化学装置的能量密度。在一些实施例中，第一活性层的内聚力为10N/m、12N/m、15N/m、18N/m、20N/m或在上述任意两个数值所组成的范围。在一些实施例中，第二活性层的内聚力为4N/m、6N/m、8N/m或在上述任意两个数值所组成的范围。
在一些实施例中，第一活性层的宽度为5mm至20mm，第二活性层的宽度为10mm至300mm。如果第一活性层的宽度太小，则其改善极片的边缘掉粉的作用相对有限；如果第一活性层的宽度太大，则在第一活性层中的粘结剂的含量较高时，会对电化学装置的体积能量密度产生不利影响。在一些实施例中，第一活性层的宽度为5mm、12mm、15mm、18mm、20mm或在上述任意两个数值所组成的范围。在一些实施例中，第二活性层的宽度为10mm、30mm、50mm、80mm、100mm、120mm、150mm、180mm、300mm或在上述任意两个数值所组成的范围。
在一些实施例中，第一活性层与集流体之间的粘结力大于第二活性层与集流体之间的粘结力。如此，使得第一活性层更不容易从集流体脱落，更稳定地发挥改善极片的边缘掉粉的作用。
在一些实施例中，第一活性层与集流体之间的粘结力为8N/m至20N/m， 第二活性层与集流体之间的粘结力为1N/m至8N/m。如果第一活性层与集流体之间的粘结力太小，则第一活性层容易从集流体脱落，进而影响第一活性层的改善极片边缘掉粉的作用的发挥；如果第一活性层与集流体之间的粘结力太大，则通常要求第一活性层中的较高的粘结剂含量，从而不利于提升电化学装置的体积能量密度。在一些实施例中，第一活性层与集流体之间的粘结力为8N/m、10N/m、12N/m、15N/m、18N/m、20N/m或在上述任意两个数值所组成的范围。在一些实施例中，第二活性层与集流体之间的粘结力为1N/m、3N/m、5N/m、6N/m、8N/m或在上述任意两个数值所组成的范围。
在一些实施例中，第一活性层包括第一活性材料和第一粘结剂，第二活性层包括第二活性材料和第二粘结剂，第一活性材料的粉体压实密度大于第二活性材料的粉体压实密度。粉体压实密度越大，表明在单位体积内，使用相同的压力，这种活性材料具有更高的重量。因此，在进行压实时，在相同的冷压条件小，由于位于极片边缘的第一活性材料具有更高的粉体压实密度，因此，极片边缘因为可以容纳更多的第一活性材料而不会掉粉。这种条件下，可以增大压实过程中的压力，在压力增大的情况下，极片也不会出现边缘掉粉的现象，从而可以提高单位面积涂覆重量，极片的压实密度得到提高，有利于增加电化学装置的能量密度。
在一些实施例中，第一粘结剂在第一活性层中的质量分数大于第二粘结剂在第二活性层中的质量分数。通过使第一粘结剂在第一活性层中的质量分数大于第二粘结剂在第二活性层中的质量分数，更多的粘结剂会使得活性材料颗粒与活性材料颗粒之间具有更好的粘结，可以使得第一活性层的内聚力大于第二活性层的内聚力。
在一些实施例中，第一活性材料的粉体压实密度为1.8g/cm 3至2.5g/cm 3，第二活性材料的粉体压实密度为1g/cm 3至1.7g/cm 3。通过使第一活性材料的粉体压实密度大于1.8g/cm 3，可以改善极片的边缘掉粉现象；然而，在第一活性材料的粉体压实密度过大时，例如，大于2.5g/cm 3，可能不利于电解液的浸润。在一些实施例中，第一活性材料的粉体压实密度为1.8g/cm 3、2.0g/cm 3、2.2g/cm 3、2.5g/cm 3或在上述任意两个数值所组成的范围。在一些实施例中，第二活性材料的粉体压实密度为1g/cm 3、1.2g/cm 3、1.5g/cm 3、 1.7g/cm 3或在上述任意两个数值所组成的范围。
在一些实施例中，第一粘结剂在第一活性层中的质量分数为15％至30％，第二粘结剂在第二活性层中的质量分数为1％至10％。如果第一粘结剂在第一活性层中的质量分数太小，则不利于第一活性层的内聚力的提升，改善极片的边缘掉粉的作用相对有限；如果第一粘结剂在第一活性层中的质量分数太大，则会不利于电化学装置的体积能量密度的提升。在一些实施例中，第一粘结剂在第一活性层中的质量分数为15％、20％、25％、30％或在上述任意两个数值所组成的范围。在一些实施例中，第二粘结剂在第二活性层中的质量分数为1％、3％、5％、8％、10％或在上述任意两个数值所组成的范围。
在一些实施例中，第一极片为负极极片，活性层为负极活性层，集流体为负极集流体，负极集流体可以采用铜箔、铜合金箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、复合集流体或碳基集流体中的至少一种。对应的，第二极片为正极极片。通过改善负极极片的边缘掉粉现象，可以增加负极活性材料在极片边缘的单位面积涂覆重量，为锂离子的嵌入和脱出提供更多的位置，从而降低负极极片的边缘析锂风险，并有利于提高电化学装置的能量密度。
在一些实施例中，第一活性材料和第二活性材料各自独立地包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、硅氧化物(如SiO x(0＜x＜2))、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、钛酸锂、Li-Al合金或金属锂中的至少一种。
在一些实施例中，第一极片为正极极片，活性层为正极活性层，集流体为正极集流体，正极集流体包括铝箔。对应的，第二极片为负极极片。通过改善正极极片的边缘掉粉现象，可以增加正极活性材料在极片边缘的单位面积涂覆重量，提高了锂离子的数量，从而有利于增加电化学装置的能量密度。
在一些实施例中，第一活性材料和第二活性材料各自独立地包括钴酸锂、磷酸铁锂、磷酸锰铁锂、磷酸铁钠、磷酸钒锂、磷酸钒钠、磷酸钒氧锂、磷酸钒氧钠、钒酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、富锂锰基材料或镍钴铝酸锂中的至少一种。
在一些实施例中，第一粘结剂和第二粘结剂各自独立地包括聚丙烯醇、 聚丙烯酸、聚丙烯酸盐、聚酰亚胺、聚酰胺酰亚胺、丁苯橡胶、聚偏氟乙烯、聚偏二氟乙烯、聚四氟乙烯、聚乙烯醇缩丁醛、水性丙烯酸树脂或羧甲基纤维素盐中的至少一种。
在一些实施例中，第一活性层和第二活性层还各自包括导电剂。在一些实施例中，导电剂包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。
在一些实施例中，极耳与集流体101一体成型。如此，有利于简化电化学装置的制备工艺，并且也有利于极耳的稳定连接。
在一些实施例中，电化学装置还可以包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的至少一种。在一些实施例中，电解液包括锂盐和非水溶剂。在一些实施例中，锂盐可以包括LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或二氟硼酸锂等中的至少一种。非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物或其它有机溶剂等中的至少一种。
在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘结性。
在本申请的一些实施例中，通过将第一极片、隔离膜和第二极片层叠后进行卷绕得到卷绕式电极组件，从而制备电化学装置。在一些实施例中，通 过将第一极片、隔离膜和第二极片进行堆叠后得到叠片式电极组件，从而制备电化学装置。
在一些实施例中，电化学装置包括锂离子电池，但是本申请不限于此。
在本申请的一些实施例中，以锂离子电池为例，将正极极片、隔离膜、负极极片制备为卷绕式电极组件，之后装入例如铝塑膜中进行封装，注入电解液，化成、封装，即制成锂离子电池。然后，对制备的锂离子电池进行性能测试。
本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请的实施例还提供了包括上述电化学装置的电子装置。本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、无人机、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
实施例1
正极极片的制备：将正极活性材料钴酸锂、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97∶1.4∶1.6进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，搅拌均匀。将浆料(固含量为72wt％)均匀涂覆在正极集流体铝箔上，涂覆厚度为80μm，在85℃下烘干，然后经过冷压、裁片、分切后，在85℃的真空条件下干燥4小时，得到正极极片。
负极极片的制备：将负极活性材料天然石墨、分散剂羧甲基纤维素锂、粘接剂聚丙烯酸以8∶0.2∶1.8的重量比例加水进行搅拌，直至浆料分散均匀， 得到第一浆料。将负极活性材料天然石墨、分散剂羧甲基纤维素锂、粘接剂聚丙烯酸以9∶0.2∶0.8的重量比例加水进行搅拌，直至浆料分散均匀，得到第二浆料。采用10μm厚度铜箔作为负极集流体，采用斑马涂布工艺(即间隔涂布)，将第一浆料和第二浆料分别涂覆于负极集流体的表面形成涂覆区，并露出未涂覆第一浆料和第二浆料的空箔区，第一浆料位于第二浆料靠近空箔区的一侧，即第二浆料位于涂覆区的边缘，涂覆厚度为50μm，在85℃下烘干，然后经过冷压、裁片、分切后，对空箔区进行模切极耳，进一步地，在120℃的真空条件下干燥12小时，得到负极极片。
隔离膜的制备：隔离膜为7μm厚的聚乙烯(PE)。
电解液的制备：在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)按照质量比为EC∶PC∶DEC＝1∶1∶1进行混合，溶解并充分搅拌后加入锂盐LiPF6，混合均匀后获得电解液，其中LiPF6的浓度为1mol/L。
锂离子电池的制备：将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正极极片和负极极片中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
其他实施例和对比例是在实施例1的步骤的基础上进行参数变更，具体变更的参数如下所述。
实施例2与实施例1的不同仅在于第一浆料的组成，为：天然石墨、分散剂羧甲基纤维素锂、粘接剂聚丙烯酸的重量比例为7.8∶0.2∶2。
实施例3与实施例1的不同仅在于第一浆料的组成，天然石墨、分散剂羧甲基纤维素锂、粘接剂聚丙烯酸的重量比例为7.6∶0.2∶2.2。
实施例4与实施例1的不同在于第二浆料中的分散剂为羧甲基纤维素钠，粘结剂为丁苯橡胶；另外，第一浆料的组成不同，为：人造石墨、分散剂羧甲基纤维素钠、粘接剂丁苯橡胶的重量比例为9∶0.2∶0.8，人造石墨的粉体压实密度为1.85g/cm 3。
实施例5与实施例4的不同仅在于人造石墨的粉体压实密度为1.95g/cm 3。
实施例6与实施例4的不同仅在于人造石墨的粉体压实密度为2g/cm 3。
实施例7与实施例1的不同在于第一浆料的组成不同，为：人造石墨、分散剂羧甲基纤维素钠、粘接剂丁苯橡胶的重量比例为8∶0.2∶1.8，人造石墨的粉体压实密度为1.85g/cm 3。
实施例8与实施例7的不同仅在于人造石墨的粉体压实密度为2g/cm 3。
对比例1在负极集流体上仅涂布第二浆料，未涂布第一浆料从而使，第二浆料的组成为：天然石墨、分散剂羧甲基纤维素钠、粘接剂丁苯橡胶的重量比例为9∶0.2∶0.8，人造石墨的粉体压实密度为1.65g/cm 3。
对比例2与对比例1的不同仅在于第二浆料的活性材料由天然石墨更改为硬碳，且硬碳的粉体压实密度为1.2g/cm 3。对比例3与对比例1的不同仅在于第二浆料中的粘结剂由丁苯橡胶更改为聚丙烯酸钠。
下面描述本申请的各个参数的测试方法。
1.负极活性层与负极集流体粘结力测试：
负极活性层与负极集流体的粘结力测试所用仪器的品牌为Instron，型号为33652，取负极(宽30mm×长度(100mm至160mm))，用双面胶纸(型号：3M9448A，宽度20mm×长度(90mm至150mm))固定于钢板上，将与负极等宽的纸带与负极一侧用胶纸固定，调整拉力机限位块至合适位置，将纸带向上翻折及滑移40mm，滑移速率为50mm/min，测试180°下(即反方向拉伸)负极活性层与负极集流体之间的粘结力。
2.内聚力测试方法：
取干燥后的极片，用刀片截取宽30mm×长度(100mm至160mm)的试样。将专用双面胶贴于钢板上，胶带宽度20mm×长度(90mm至150mm)。将极片试样贴在双面胶上，测试面朝下。再将绿胶(宽度20mm×长度(90mm至150mm)，紧贴于极片表面。将宽度与极片等宽，长度大于试样长度80mm至200mm的纸带插入绿胶下方，并且用皱纹胶固定。打开三思拉力机电源，指示灯亮，调整限位块到合适位置，将绿胶向上翻折及滑移40mm，滑移速率为50mm/min，测试180°下(即反方向拉伸)负极活性层之间的内聚力。
3.粉体压实密度测试
从极片上刮粉并烧结，获得活性材料粉体，放置到粉体密度测试仪模具中(测试模具(CARVER#3619(13mm))；测试设备为三思纵横UTM7305，模具放于设备的上下压盘的中间处，点击设备中的运行键，设备将按照设置的参数运行，当从设备压力点卸压到5T时记录此时位移数值，此为该样品在此压力下的厚度(升压速率为10mm/min，升压保持时间为30s，泄压速率为30mm/min，泄压保持时间为10s)。其中，粉体的压实密度可通过以下公式计算：
ρc＝m/V＝m/S*H，
式中：ρc-----粉末的压实密度，g/cm3；
m-----称取物料的质量，g；
S-----模具底面积，cm2；
H-----压实后的高度，cm。
4.粘接剂含量测试方法
从极片上刮粉，将粉末至于热重测试仪中，设置温度范围20～500℃，升温速率5℃/min，气体氛围为空气，然后运行设备温度200～400℃之间出现重量降低，该减少的重量所占的重量百分比即为粘接剂含量。
表1示出了相应实施例1至8和对比例1至3的各个参数和评估结果。
Figure PCTCN2021111736-appb-000001
Figure PCTCN2021111736-appb-000002
通过比较实施例4和对比例1可知，相对于仅含有第二活性层的负极极片，通过设置额外的第一活性层，并且使第一活性层的内聚力大于所述第二活性层的内聚力，能够明显改善负极极片的边缘掉粉情况。
通过比较实施例1至3可知，当第一活性层中的活性材料相同时，随着第一活性层中的粘结剂用量的增大，第一活性层的内聚力和粘结力越大，并且负极极片几乎不掉粉。
通过比较实施例4至6可知，在第一活性层中的各组分的含量相同的情况下，第一活性层中的第一活性材料的粉体压实密度越大，内聚力和粘结力越大，并且负极极片几乎不掉粉。
通过比较实施例1-6和实施例7-8可知，第一活性层中的第一活性材料的粉体压实密度越大，粘结剂用量越大，内聚力和粘结力会越大，并且此时负极极片不发生掉粉。
在对比例1-3中，在集流体的中间和边缘设置相同的活性层时，会发生明显掉粉。在对比例2中，相对于对比例1，在第一活性层的活性材料的种类、粉体压实密度变化时，仍然会发生明显掉粉。在对比例3中，相对于对比例1，在第一活性层中的粘结剂变化时，也仍然会发生明显掉粉。由此可见，当第一活性材料的粉体压实密度较低，第一活性中的粘结剂的用量较少，极片边缘容易掉粉。
以上描述仅为本申请的较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本申请中所涉及的公开范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖由上述技术特征或其等同特征进行任意组合而形成的其它技术方案。例如上述特征与本申请中公开的具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (10)

  1. 一种电化学装置，包括第一极片、与第一极片电性不同的第二极片和设置于所述第一极片与所述第二极片之间的隔离膜，其中，所述第一极片包括：
    集流体；
    极耳，与所述集流体电连接并伸出于所述集流体；
    活性层，设置于所述集流体的表面，所述活性层包括第一活性层和第二活性层，沿第一方向，所述第一活性层位于所述第二活性层朝向所述极耳的一侧，并与所述第二活性层相邻接或部分重叠，沿第二方向，所述第一活性层和第二活性层呈带状延伸设置；其中，所述第一活性层的内聚力大于所述第二活性层的内聚力；
    在三维直角坐标系中，所述第一方向为所述极耳伸出所述集流体的方向，第三方向为所述负极极片的厚度方向，所述第二方向垂直于所述第一方向和第二方向所在的平面。
  2. 根据权利要求1所述的电化学装置，其中，所述第一活性层的内聚力为10N/m至20N/m，所述第二活性层的内聚力为4N/m至8N/m。
  3. 根据权利要求1所述的电化学装置，其中，所述第一活性层的宽度为5mm至20mm，所述第二活性层的宽度为10mm至300mm。
  4. 根据权利要求1所述的电化学装置，其中，所述第一活性层与所述集流体之间的粘结力大于所述第二活性层与所述集流体之间的粘结力。
  5. 根据权利要求1所述的电化学装置，其中，所述第一活性层与所述集流体之间的粘结力为8N/m至20N/m，所述第二活性层与所述集流体之间的粘结力为1N/m至8N/m。
  6. 根据权利要求1所述的电化学装置，其中，所述第一活性层包括第一活性材料和第一粘结剂，所述第二活性层包括第二活性材料和第二粘结剂，所述第一活性材料的粉体压实密度大于所述第二活性材料的粉体压实密度，和/或，所述第一粘结剂在所述第一活性层中的质量分数大于所述第二粘结剂在所述第二活性层中的质量分数。
  7. 根据权利要求6所述的电化学装置，其中，所述第一活性材料的粉体压实密度为1.8g/cm 3至2.5g/cm 3，所述第二活性材料的粉体压实密度为1g/cm 3至1.7g/cm 3，和/或，所述第一粘结剂在所述第一活性材料层中的质量分数为15％至30％，所述第二粘结剂在所述第二活性材料层中的质量分数为1％至10％。
  8. 根据权利要求6所述的电化学装置，其中，所述第一活性材料和所述第二活性材料各自独立地包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、硅氧化物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、钛酸锂、Li-Al合金或金属锂中的至少一种；所述第一粘结剂和所述第二粘结剂各自独立地包括聚丙烯醇、聚丙烯酸、聚丙烯酸盐、聚酰亚胺、聚酰胺酰亚胺、丁苯橡胶、聚偏氟乙烯、聚偏二氟乙烯、聚四氟乙烯、聚乙烯醇缩丁醛、水性丙烯酸树脂或羧甲基纤维素盐中的至少一种。
  9. 根据权利要求1所述的电化学装置，其中，所述极耳与所述集流体一体成型。
  10. 一种电子装置，包括根据权利要求1至9中任一项所述的电化学装置。
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